Gumtree is full of covers bands or really dreadful deluded guitarists who can't play and bad drummers who want to be session drummers. It's best to put an advert in rough trade or denmark street or a rehearsal place.

idea is to put up flyers in music colleges near you, the musicians are usually pretty great and have often never been in rock bands before so you can boss them around. That is if you dont mind having young uns in your band.

Forming Bands is probably the best directory (eg. it lists 63 drummers for Manchester, 43 punk bands, 55 bassists. Bandvacancies has 14 listings in total for the city and isn't searchable). Musolist is ok. Musicians In Your City is okish until they ask you to pay to make contact. Gumtree is good for seeing who's around now.

They're all a waste of time compared to getting out and talking to people.